Current Transformers

Current transformers (CT) are devices that are used to transform the current from a high current into a lower current so that the power can then be measured and controlled. The transformers consist of a core, a primary and a secondary winding. When an alternating current flows through the primary winding, a magnetic flux is created which then induces an alternating current in the secondary winding. This alternating current is proportional to the current in its primary. Current transformers are also known as a "step-down transformers". Once the current has been reduced it can be safely monitored and measured using an ammeter.


Current transformers can perform circuit control and perform roles for safety protection and current limiting.


Current transformers are found in:


  • Generating stations,

  • Electrical substations

  • Commercial electric power distribution.

Types of Current Transformers


Toroidal Current Transformer - These transformers are shaped like a doughnut they do not contain a primary winding. Instead, the line that carries the current flowing in the network is threaded through a window or hole in the toroidal transformer. Toroidal transformers offer high efficiency with minimal excess noise and little excess leakage inductance.


Wound Current Transformer - The transformers primary winding is physically connected in series with the conductor that carries the measured current flowing in the circuit. The magnitude of the secondary current is dependent on the turns ratio of the transformer.


Bar-type Current Transformer – This type of current transformer uses the actual cable or bus-bar of the main circuit as the primary winding, which is equivalent to a single turn. They are fully insulated from the high operating voltage of the system and are usually bolted to the current carrying device.


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Description Price Current Ratio Inner Diameter Transformer Type Overall Height Overall Width Input Current Overall Depth Output Current Minimum Temperature Maximum Temperature Dimensions For Use With Mounting Type Priced to Clear
RS Stock No. 124-3895
BrandRS PRO
£8.56
Each
Units
- - - - - 200 → 500A - - -55°C +130°C 55.6 x 20.6 x 55.6 mm - PCB Mount -
RS Stock No. 173-0045
BrandRS PRO
£1.827
Each (In a Box of 351)
Units
- - - - - 15A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3881
BrandRS PRO
£2.02
Each
Units
- - - - - 15A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0236
BrandRS PRO
£1.405
Each (In a Box of 351)
Units
- - - - - 15A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3901
BrandRS PRO
£1.34
Each
Units
- - - - - 15A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0216
BrandRS PRO
£2.676
Each (In a Box of 351)
Units
- - - - - 7.5A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3899
BrandRS PRO
£2.94
Each
Units
- - - - - 7.5A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0184
BrandRS PRO
£4.355
Each (In a Box of 98)
Units
- - - - - 5 → 50A - - -40°C +120°C 32 x 20.5 x 35 mm - PCB Mount -
RS Stock No. 124-3883
BrandRS PRO
£4.81
Each
Units
- - - - - 5 → 50A - - -40°C +120°C 32 x 20.5 x 35 mm - PCB Mount -
RS Stock No. 173-0197
BrandRS PRO
£3.444
Each (In a Box of 176)
Units
- - - - - 25 → 75A - - -55°C +130°C 30.2 x 14.3 x 30.2 mm - PCB Mount -
RS Stock No. 173-0235
BrandRS PRO
£2.995
Each (In a Box of 351)
Units
- - - - - 10A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3900
BrandRS PRO
£3.31
Each
Units
- - - - - 10A - - -40°C +120°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 124-3888
BrandRS PRO
£3.78
Each
Units
- - - - - 25 → 75A - - -55°C +130°C 30.2 x 14.3 x 30.2 mm - PCB Mount -
RS Stock No. 173-0237
BrandRS PRO
£3.474
Each (In a Box of 351)
Units
- - - - - 10 → 20A - - -40°C +85°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0199
BrandRS PRO
£2.258
Each (In a Box of 133)
Units
- - - - - 40 → 125A - - -55°C +130°C 34.9 x 14.3 x 34.9 mm - PCB Mount -
RS Stock No. 124-3890
BrandRS PRO
£2.51
Each
Units
- - - - - 40 → 125A - - -55°C +130°C 34.9 x 14.3 x 34.9 mm - PCB Mount -
RS Stock No. 124-3903
BrandRS PRO
£3.82
Each
Units
- - - - - 10 → 20A - - -40°C +85°C 17.2 x 9.53 x 20.4 mm - PCB Mount -
RS Stock No. 173-0238
BrandRS PRO
£2.192
Each (In a Box of 220)
Units
- - - - - 50A - - -40°C +85°C 23.8 x 11.12 x 23.8 mm - PCB Mount -
RS Stock No. 124-3902
BrandRS PRO
£2.44
Each
Units
- - - - - 50A - - -40°C +85°C 23.8 x 11.12 x 23.8 mm - PCB Mount -
RS Stock No. 124-3891
BrandRS PRO
£2.24
Each
Units
- - - - - 50 → 125A - - -55°C +130°C 34.9 x 14.3 x 34.9 mm - PCB Mount -
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